What To Wear Under a Wetsuit For Warmth

Sometimes when you're diving, surfing or doing some other water sport or activity your wetsuit just isn't keeping you warm enough and you find yourself getting extremely cold.

You may not want to upgrade to a newer thicker warmer wetsuit right now and want to know what to wear under a wetsuit for warmth.

While the best option is usually always “get a thicker and better fitting wetsuit” there are some things you can wear under a wetsuit that will keep you that little bit warmer.


Below we'll look in more detail at some of the options for things you can wear under your wetsuit to add some warmth and stop you from getting cold as quickly.

Firstly, Does Your Wetsuit Fit Properly?

Before we jump into the different things you can wear under your wetsuit to keep you warm I firstly want to check you've got a wetsuit that fits you properly.

A lot of people unknowingly buy a wetsuit that is too big for them.

This is because wetsuits expand in the water and also expand overtime so the wetsuit almost needs to feel too tight in the store to be the right fit.

If you've got rolls of fabric under your arms, if the arms/legs are a bit too long or if you've got empty air space at the small of back you may have a wetsuit that's too big for you.

A wetsuit that's too big won't work properly. It'll let in too much water too quickly (called the dreaded “flush”) and it'll keep too much water in your wetsuit which your body has to heat up.

Below is a good video guide on choosing the right size wetsuit for you.

Ok, now let's have a look at what you can wear under your wetsuit to add some warmth and keep you warmer.

Thermal Rash Vest

There are a variety of different thermal rash vests out there that are designed to either keep you slightly warmer when the water is a mice temperature or they are designed to be used under wetsuits for extra warmth.

These are usually 0.5-1mm in thickness and made from either neoprene like wetsuits or some other insulating material. Some even have metallic interior to help reflect the infrared heat your body gives off back onto you.

The key here is you are generally trying to keep your core warm, so a focus on your internal organs.

So you may just use a sleeveless vest or you may use a short sleeve t-shirt or you may move up to a long sleeve t-shirt or you can even get full body suits for extra warmth.

There are a bunch of brands out there but the ones I see recommended the most by people who use them are Lavacore, Sharkskin and Farmer John.

Lavacore say this about their products on their about page:

Lavacore is a technically advanced fabric, constructed and engineered exclusively for water sports requiring the ultimate in thermal control and superior comfort.
Thermal and neutral buoyancy properties create the ideal garment – under a neoprene wetsuit for added insulation and warmth or as a stand alone exposure protection garment. The unique design of Lavacore materials eliminates constriction and allows for extreme movement and flexibility while regulating your core warmth.

See different products available from Lavacore at Amazon

Hooded Vest

A step up from a just a regular rash vest is a hooded rash vest that covers both your body and your face.

The products from Lavacore are designed to reduce windchill whereas regular wetsuits often aren't so this can add a decent amount of insulation when worn under your wetsuit.

Neoprene Swimwear

Similar to a rash vest or t-shirt but designed more for solo swimwear, neoprene swimsuits can provide an extra layer of insulation under your wetsuit.

For females wearing a one piece swimming costume this can help protect and insulate the core and keep you warmer for longer.

Polyester Long Johns and Socks

This one I'm not so sure about but I saw an extremely talented diver and someone who dives UNDER ICE recommend this so I have to throw it in here.

He personally wears polyester long johns and socks under his wetsuit and wetsuit booties and feels it makes a difference.

Recommended by ice water diver Darrin Jillson this is what he says about polyester long johns and socks under his wetsuit here:

The biggest myth in wetsuits is that the water between the wetsuit and your skin is what keeps you warm. For cold water diving I will wear polyester long johns and socks under it. I think it makes a difference, but I have had arguments with others who say it can’t help.

I also did some more digging and found a few people saying that yes, even when wet polyester and other synthetic fabrics can keep you warm.

Check out this response from this forum thread:

One March day I was paddling in New Jersey and flipped over. The air was about 50 degrees with a light wind. I was wearing a polarfleece ( synthetic) jacket. Fortunately I was paddling in a tidal creek(only 50 yards wide) and could swim and walk quickly to the bank, empty the kayak and reenter. It wasn’t until the next day that I realized I had not felt the cold. Adrenaline? Certainly not when paddling a half mile back to the put in. I credit the polar fleece for keeping me warm in spite of being soaked.

I personally would assume they wouldn't keep you as warm when wet as they would when dry but would likely help a little bit.

They would be a little bit insulating and they would also restrict the movement of water inside your wetsuit, stopping cold water from flushing out the hot water as quickly.

They may also make your wetsuit tighter which could also work to keep you warmer.

If you've got some lying around they are worth a try or you can buy them super affordably. It's way cheaper than a brand new wetsuit so worth a go in my opinion.

See some affordable thermal underwear options at Amazon

Reusable Instant Heat Packs

You can purchase reusable waterproof heat packs that you activate by clicking a metal activator inside.

When activated the heat packs heat up to around 140ºF (60ºC) or about the temperature of a hot cup of coffee.

Some surfers and divers use these inside their wetsuits to keep them that little bit warmer on those extra cold days.

You want to focus them around your core, keeping your internal organs warm, and you also want to make sure that you don't have them against your bare skin or they can burn you.

So people wrap them in a rash suit material for this reason.

You can activate them just before entering the water or it might even be a better idea to wait until you're in the water, your body has warmed up the cold water in your wetsuit already and then activate them.

Some people say they work a little bit, others question whether they work at all. However, it can be a good cheap reusable solution to keep you just a little bit warmer.

See the latest price of Instant Reusable Heat Packs at Amazon

There is also an amazing video about how these work which you can watch below:

Battery Operated Heated Vests

For those diving or surfing in extremely cold conditions there are now battery operated heat vests.

These use rechargeable batteries and a material that is able to emit infrared heat the penetrates deep into your core warming up your body and keeping you from getting too cold.

These don't come cheap and are really only for the super serious diver or surfer who is pushing the edge and going out in the most extreme conditions.

You can find these on places like HeatedWetsuits.com

Here – Thermalution Deep Diver 70m Undersuit

Wear a Hoodie, Gloves and Booties For Extra Warmth

While not technically something you wear “under” your wetsuit adding a wetsuit hoodie, gloves and booties can give you a massive boost in how warm you'll feel in the water.

They obviously protect and insulate the areas of your body that a traditional wetsuit doesn't cover but they also form a tighter seal around your neck, wrists and ankles which is where the bulk of the cold water enters your wetsuit.

This means less cold water will be getting into your wetsuit and you'll be staying warmer for longer.

They are also good accessories as you don't have to buy an entirely new wetsuit. You can use them all in the colder months, then maybe drop down to just booties or just a hoodie and as the water gets warmer you can go back to just using your wetsuit.

Pour Hot Water Into Your Suit Before Going In The Water

In a previous article I've gone into detail on how to stay warm in a wetsuit, but one of the best things you can do is to fill up your wetsuit with warm water before you go into the cold.

Personally I use warm tap water and fill up a Hydro Flask or other insulated bottle. When I get down to the beach I'll put on my wetsuit and then fill up the inside with warm water before I go into the ocean.

This makes the moment when you enter the water so much more pleasant as your wetsuit isn't instantly filled from top to toe with cold water.

Consider a Thicker Wetsuit or Drysuit

If you've found wearing things under your wetsuit still isn't doing enough to keep you warm then it may be time to consider getting a thicker wetsuit that is going to keep you warmer.

Or so some water activities or extremely cold conditions a dry suit may be a better option for you and allow you to stay warmer.

Below is a handy guide for roughly what thickness and length of wetsuit you'll want based off what water temperature you're swimming in.

Water Temp Range ºF (ºC)Wetsuit ThicknessRecommended Wetsuit TypeSeal Type
>72ºF (>22ºC)N/ARashguardN/A
65-75ºF (18-24ºC)0.5 – 2/1 mmTop / Spring Suit / Shorty / Short JohnN/A
62-68ºF (16-20ºC)2 – 3/2 mmSpring Suit / Steamer (Full Suit)Flatlock
58-63ºF (14-17ºC)3/2 – 4/3 mmSteamer, BootsSealed
52-58ºF (11-14ºC)4/3 – 5/4/3 mmSteamer, Boots, Gloves, HoodSealed + Taped
43-52ºF (6-11ºC)5/4 – 5/4/3 mmSteamer, Boots, Gloves, HoodSealed + Taped
<42ºF (<6ºC)6/5 – 7 mmSteamer, Boots, 3 Finger Gloves, HoodSealed + Taped